In order to determine the role of human papillomaviruses (HPVs) in oral tumors, biopsy samples from patients with oral leukoplakias and squamous cell carcinomas will be collected and analyzed for the presence and type of HPV DNA by Southern blot hybridization and/or in situ cytohybridization. Clinical histories will be obtained from the patients' medical records and histopathology of the biopsies will be performed. DNA probes to identify HPV types 2, 5, 6, 8, 11, 13, 16, and 18 will be used for Southern blot hybridization and in the development of a reproductible and sensitive in situ cytohybridization assay using 35S or biotinylated labels. The in situ cytohybridization technique will be further refined to probe for specific subgenomic messenger RNAs. Open translation from regions from the early and late regions of the HPV genomic types found to be prevalent in oral lesions will be cloned into a SP6 promoter vector to allow the synthesis of antisense transcription-specific probes. The hybridization of these probes will be correlated with the state of cell differentiation and the type of oral lesion. To identify HPV proteins involved in neoplasia, synthetic oligopeptides corresponding to open reading frames E6 and E5 of HPV-11 and HPV-16 will be used to produce specific antisera identifying the encoded proteins. Affinity-purified antibodies will be used in immunoperoxidase staining of histopathological sections and in immunoprecipitation of cultured cell extracts from oral lesions to identify and characterize these viral proteins.